The present disclosure relates to a delivery system for heart valve replacement and, in particular, for replacement of collapsible prosthetic heart valves. More particularly, the present disclosure relates to delivery systems for collapsible prosthetic heart valves that may be repositioned during the deployment procedure.
Prosthetic heart valves that are collapsible to a relatively small circumferential size can be delivered into a patient less invasively than valves that are not collapsible. For example, a collapsible valve may be delivered into a patient via a tube-like delivery apparatus such as a catheter, a trocar, a laparoscopic instrument, or the like. This collapsibility can avoid the need for a more invasive procedure such as full open-chest, open-heart surgery.
Collapsible prosthetic heart valves typically take the form of a valve structure mounted on a stent. There are two types of stents on which the valve structures are ordinarily mounted: a self-expanding stent and a balloon-expandable stent. To place such valves into a delivery apparatus and ultimately into a patient, the valve must first be collapsed or crimped to reduce its circumferential size.
When a collapsed prosthetic valve has reached the desired implant site in the patient (e.g., at or near the annulus of the patient's heart valve that is to be replaced by the prosthetic valve), the prosthetic valve can be deployed or released from the delivery apparatus and re-expanded to full operating size. For balloon-expandable valves, this generally involves releasing the entire valve, assuring its proper location, and then expanding a balloon positioned within the valve stent. For self-expanding valves, on the other hand, the stent automatically expands as the sheath covering the valve is withdrawn.
In conventional delivery systems for self-expanding aortic valves, for example, after the delivery system has been positioned for deployment, the annulus end of the valve is typically unsheathed and expanded first, while the aortic end of the valve remains sheathed. Once the annulus end of the valve has expanded, it may be determined that the valve needs to be repositioned in the patient's aortic annulus. To accomplish this, a user (such as a surgeon or an interventional cardiologist) typically resheathes the annulus end of the valve so that the valve can be repositioned while in a collapsed state. After the valve has been repositioned, the user can again release the valve.
Once a self-expanding valve has been fully deployed, it expands to a diameter larger than that of the sheath that previously retained the valve in the collapsed condition, making resheathing difficult. In order for the user to be able to more readily resheathe a valve, it is preferable that the valve be only partially deployed, with a portion of the valve still collapsed inside of the sheath.
Despite the various improvements that have been made to the collapsible prosthetic heart valve delivery process, conventional delivery devices, systems, and methods suffer from some shortcomings. For example, in some delivery devices for self-expanding valves, it is difficult to control how much of the valve remains in the sheath during a partial deployment, and the user may accidentally deploy the valve fully before verifying that the annulus end of the valve is in the optimal position in the patient's valve annulus, thereby taking away the opportunity to resheathe and reposition the valve. Moreover, it is difficult during prosthetic heart valve delivery to determine whether a valve assembly will function as intended without full deployment of the heart valve. Due to anatomical variations between patients, a fully deployed heart valve may need to be removed from the patient if it appears that the valve is not functioning properly. Removing a fully deployed heart valve increases the length of the procedure and increases the risk of infection and/or damage to heart tissue.
There therefore is a need for further improvements to the devices, systems, and methods for transcatheter delivery of collapsible prosthetic heart valves, and in particular, self-expanding prosthetic heart valves. Among other advantages, the present disclosure may address one or more of these needs.